The chemical substance named slow reacting substance of anaphylaxis was recognized many years ago to be involved in the profound bronchial smooth muscle contraction observed in certain asthmatic conditions. In the past year's studies of this project, a slow reacting substance has been structurally identified as a cysteinyl adduct of an arachidonic acid metabolite. This substance was obtained from murine mastocytoma cells following stimulation with the calcium ionophore A2387 after extensive isolation and purification procedures. The slow reacting substance identified has been named leukotriene C and is only one member of a family of biologically active leukotrienes. The structure of other leukotrienes from the murine masticytoma and rat peritoneal mast cells will be investigated in the proposed research. Studies are also planned with various drugs known to alter the metabolism of arachidonic acid in order to investigate the effect of these agents on leukotriene C synthesis. A second aspect of this project is the development of mass spectrometric methods of analysis of complex lipids such as phospholipid molecular species and leukotriene C. Such methods should be able to provide detailed qualitative information (structural data) as well as quantitative data through the appropriate use of stable isotope labelled internal standards. The potential usefulness of 180-labelled species in this class of compounds will be investigated.